1. Field of the Invention
This invention relates to a device for detecting the focus in a photographic and motion picture camera, and more particularly to a device for representing the condition of focus on a plane in a camera or the like to facilitate the adjustment of focus of an image formed by an objective.
2. Description of the Prior Art
It has been known in the art to focus an image formed by an objective on a focusing plate and detect the focus by viewing and measuring the sharpness of the image by eyes through a view finder system. In this kind of focus detecting device, the quantity of light is lost by the focusing plate which is generally a diffusing plate such as a ground glass. Further, it is difficult to detect the focus when the subject is dark. Particularly for the short-sighted, the detection of the focus is difficult. Although this kind of device is provided on the focusing plate with a prism for splitting image, it is sometimes insufficient in cases as above.